How James Marsters, Anthony Head and Kelly Hu will rock Warehouse 13's S4.5

Syfy's Warehouse 13 and the world barely escaped another Earth-shattering tragedy a la artifact, this time a pandemic, when the series premiered its season 4.5 last week. But don't think things are going to get easy for the Warehouse agents anytime soon, as consequences of the deeds of evil Artie reverberate and an array of notable sci-fi guest stars pop in for recurring roles, including Buffy alums James Marsters and Anthony Head and X-Men's Kelly Hu.

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“We've got to, of course, deal with the repercussions of what Artie has done,” said creator and executive producer Jack Kenny. “He killed Leena. That's going to be some pretty major stuff. But we still continue to do what we do with a sense of … I hesitate to say a sense of humor, but we do try to keep humor alive. It's not all dark and weepy and crying.”

Now that Claudia has saved Artie and he's returned to his right mind, “our next order of business is to figure out how do we move forward now, having been through what we've been through. Leena's dead. She's not coming back. It's not a sci-fi death. It's a real death. She's gone. And that was important for us to do it that way, because you don't want everybody always thinking, 'Oh, well, in sci-fi there's no jeopardy, no stakes, because you can always come back to life.' So it was important to us to have somebody die who's really dead and have her really go away,” said Kenny.

“The first journey is one of healing. Our theme for both last season and this season was dealing with various forms of mortality. Our family is pretty firm and pretty strong now. We know who we are and how we feel about each other, and there's a great deal of love and concern. So the next hurdle to throw at the family was loss and mortality. How do we deal with the loss of someone else? Our own mortality?”

That kind of loss “has a tremendously powerful effect on a family. I think it speaks to the strength of the relationships if we're able to get through it. And we will continue that. We will continue to test the bonds of our family. At the end of episode 17, we have a pretty big bomb to drop on Myka. That Myka and Pete are going to have to deal with in a major way, in a pretty powerful way. We'll get to meet an ex-flame of Steve's on a mission and see how he deals with that. Kind of an unexpected turn of events. Of course our people give him endless s--t about it,” he said.

This season there are “some really cool guest stars lined up.” Buffy's James Marsters and Caprica's Polly Walker guest-stared as Professor Sutton and Charlotte Depres last week, and they'll be recurring this season. Sutton turned out to be the 500-plus-year-old Count of St. Germain, who's in a constant battle with his ex, aka Charlotte. Unlike Leena, the Count's death at the end of the episode doesn't look like it's going to stick, considering he's immortal and all.

Marsters and Walker will “thread in and out of the season. Then the Big Bad comes in, and there's even another pickle. As you know, we like to leave you in pickles.”

Later in the season, Marsters is “going to be teaming up with another Buffy alumnus.” That turns out to be Anthony Head, who'll play the villainous Paracelsus, an alchemist. Head will guest-star in the final three episodes of the season.

And X2's Kelly Hu guest-stars as someone who comes in due to Leena's death. She joins the cast as Abigail Cho, a protégé of Mrs. Frederic. Returning guest stars include Jaime Murray as H.G. Wells and Kate Mulgrew as Jane Lattimer, who appeared in the premiere.

In season 4.5, “we go to Vegas for an episode. There's an artifact that a magician is using to levitate people. There's an artifact, an old mining lantern, that can cause the earth to swallow somebody up,” said Kenny. “There's an episode that we shot a lot of at the Niagara Falls power plant that's about an old pirate from the 1920s. He actually intercepted a warehouse ship full of artifacts and stole a bunch of them, and Artie and Pete and Myka are on a hunt to find his lair beneath the Niagara Falls power plant. Yep, searching for pirates' treasure,” said Kenny.

“It gets pretty major by the end of this next season. There's some pretty huge upheavals in the warehouse due to what this Big Bad does. It has a lot to do with Warehouse 9,” said Kenny.